Method and system for configuring a radio interface in a communication system

ABSTRACT

A method and system for configuring a radio interface between a mobile station and a base station of a time-division multiplex mobile radio telephone system for a packet data transmission, wherein, the mobile stations are additionally identified with brief identifiers and time slots for signaling for the upstream direction are allocated to the mobile stations. The allocation of one or more time slots for signaling for the upstream direction occurs according to a prescribable sequence, wherein the allocation occurs with indicator messages that contain abbreviated identifiers and time slot designations. The allocation is thus independent of a sequence of the packets data transmission from or to the mobile station.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and base station system forconfiguring a radio interface between a mobile station and a basestation of a time-division multiplex mobile radio telephone system for apacket data transmission data transmission.

2. Description of the Prior Art

Connection-oriented concepts and concepts on the basis of logicalconnections can be recoursed for the transmission of data between twopieces of communication terminal equipment. Given connection-orienteddata transmissions, physical resources between the two pieces ofcommunication terminal equipment must be offered during the entire timeof the data transmission.

A permanent offering of physical resources is not necessary given datatransmission via logical connections. An example of such a datatransmission is packet-data transmission. Here, a logical connectionbetween the two pieces of communication terminal equipment exists duringthe duration of the entire data transmission. However, physicalresources are offered only during the actual transmission times of thedata packets. This method is based on the fact that the data arecommunicated in short data packets between which longer pauses canoccur. The physical resources are available for other logicalconnections in the pauses between the data packets. Physical resourcesare saved with reference to a logical connection.

The packet data transmission method disclosed by German Letters PatentDE 44 02 930 A1 is particularly suitable for communication systemshaving physical limited resources. The physical resources in thefrequency domain—the number of frequency channels and time slots—arelimited and must be rationally utilized in, for example, mobile radiotelephone systems such as the GSM mobile radio telephone system (globalsystem for mobile communications).

The GSM mobile radio telephone system is an example of a time-divisionmultiplex mobile radio telephone system, whereby time slots within afrequency channel can be divided onto different communication terminalequipment. The network-side radio station of a mobile radio telephonenetwork is a base station that communicates with mobile stations via aradio interface. The transmission from a mobile station to the basestation is referred to as upstream direction; the transmission from thebase station to a mobile station is referred as downstream direction. Achannel that is reserved for the packet-data transmission is formed byat least one time slot per time-division multiplex frame. Further, thecarrier frequency and, potentially, a frequency skip sequence identifythe channel.

The GSM mobile radio telephone system was originally designed for thetransmission of voice, whereby a channel was reserved for the constantinformation transmission between mobile station and base station. Inpacket data transmission, however, a common channel is used forpacket-data transmission for a plurality of mobile stations. Signalinginformation, for which a time slot is provided within the channel atcyclical intervals, is transmitted in addition to the packet data.

What the distinction in the logical and physical connections yields isthat a logical connection in fact exists for a mobile station but nopacket data is transmitted over a certain time span. Measurements of thebase station with respect to the transmission conditions of the mobilestation, however, are not possible as long as no transmission isoccurring from the mobile station to the base station. Previouslycalculated values become invalid and must be re-identified given arenewed allocation of physical channels or, respectively, the basestation must assure that the transmission conditions are set such that aprotected transmission is possible in any case. This latter situation,for example, leads to an elevated or even maximum transmission powersetting.

The present invention, therefore, is based on the object of specifying amethod and a system with improved configuration of an air interface forpacket data transmission.

SUMMARY OF THE INVENTION

Pursuant to the present invention, the mobile stations are identifiedwith abbreviated identifiers. In the method for configuring the radiointerface, time slots for signaling for the upstream direction areallocated to the mobile stations. The allocation of one or more timeslots for signaling for the upstream direction occurs according to aprescribable sequence, wherein the allocation occurs with indicatormessages that contain abbreviated identifiers and time slotdesignations. The allocation is thus independent of a sequence of thepacket data transmission from or to the mobile station.

As a result of a flexible allocation of a time slot for signaling even,a for mobile stations to which no physical channel is allocated at themoment, the base station can implement a continuous measurement to theradio interface. Given re-assumption of the packet data transmission,valid measured values are thus immediately available for configuring theradio interface.

According to a further advantageous development, the abbreviatedidentifiers of the mobile stations are selected in addition to theiridentifications within the mobile radio telephone system for the packetdata transmission. The abbreviated identifiers enable an improvedresource utilization between the network and the mobile stations via theradio interface to since they are independent of addresses for themobile stations known in the network, and the signaling is flexiblydesigned according to individual requirements independently of thepacket data transmission.

In a further development of the method for configuring the radiointerface, configuration data with respect to the radio interface for aplurality of mobile stations are combined and transmitted in a time slotfor signaling. Such a signaling is of significance for the downstreamdirection since information for configuring the radio interface for themobile station, for example the values related to the transmission powersetting or, respectively, the timing advance for the transmission time,is contained in it. Since only a few particulars are required per mobilestation, a combining of the configuration data in one message savestransmission capacity that is now available for neighboring cellmeasurements or for some other kind of signaling information.

The configuration data for a mobile station can be transmitted togetherwith the configuration data for other mobile stations in a single timeslot for signaling in a downstream direction, advantageously repeated orprovided with a coating or error recognition in this case, or in aplurality of non-successive time slots for signaling. In the latterinstance, the nesting provides protection against error. Which timeslots are combined to form such a signaling block can be set. Given sucha utilization of, for example, a second time slot for signaling, theintervening time slots can be utilized for neighboring cellmeasurements.

The portion of time slots for the neighboring cell measurements can beincreased further when less configuration data (for example, only thetiming advance) is transmitted or, respectively, when only few mobilestations are to be covered. A cyclical adaptation of the sequence of thecombining thereby can be provided. Such an adaptation creates animproved matching of the signaling outlay to the actual requirements ofthe mobile stations for a packet data transmission. The closed controlcircuit for the timing advance can be achieved according to the presentinvention, since mobile stations have time slots allocated to them forsignaling in the upstream direction and signaling blocks for the mobilestations arrive in downstream direction with a short delay time. Onlythe mobile station and the base station advantageously participate inthis control circuit. Since, differing from packet data transmission, noconcrete allocation between a mobile station and a data block (which isusually implemented in a base station controller) is needed for thissignaling, the base station can undertake the setting of the timingadvance by itself. Signaling outlay between the base station and thebase station controller is thereby eliminated.

According to a further development of the present invention, theconfiguration for the timing advance occurs independent of thetransmission power setting. The timing advance is defined according to aclosed control circuit between mobile station and base station, whereina longer cycle can be provided between two determinations on the basisof a suitable selection of the time slots for signaling. The timingadvance has to be identified only at a spacing of a few seconds in viewof the slow movement of the mobile station relative to the signalpropagation speed.

In the determination of the transmission power setting of the basestation, the transmission power is advantageously directed onto themobile station with the poorest transmission correction on the commonchannel. Open or closed control circuits can be established for thispurpose independently of a determination of the timing advance. Givengreat differences between the transmission power required for individualmobile stations and given a presence of a plurality of common channels,it is advantageous to allocate the mobile stations to the channelsaccording to the required transmission power.

Advantageously, the packet data transmission in each transmissiondirection, i.e. in upstream direction and downstream direction, occursindependently of one another. Consequently, a mobile station cantransmit data in upstream direction or receive data from the network indownstream direction. A packet data transmission in both directions alsocan be provided for a mobile station. The separation into upstream anddownstream direction enables a great flexibility in the utilization ofthe radio-oriented resources and, of course, in the design of the mobilestation as well, which potentially only transmits or receives.

Advantageously, a closed message is communicated to the base stationfrom a mobile station within a time slot for signaling. This closedmessage contains, for example, reception values of the mobile stationfor signals of the base station, as a result whereof an immediatetransmission power setting of the base station is possible given apacket data transmission in downstream direction. In that one closedmessage is communication per time slot, the time until the receptionlevel of the mobile station is present at the base station and the timefor the configuration of the radio interface are shortened. The basestation determines the timing advance or, respectively, the receptionlevel of the base stations with reference to the respective mobilestation from transmissions for signaling in upstream direction.

The specific value or values or, respectively, control values for thetiming advance and the transmission power are communicated to the mobilestation in downstream direction, whereupon this also can undertake thenecessary settings for configuration of the radio interface.

The configuring is accelerated further when the determination of thetiming advance and/or of the reception level of the base station isadditionally undertaken from the time slots for the packet datatransmission. The allocation of abbreviated identifiers to mobilestations can also influence the setting time of the configuration. Thesetting time is shortened, for example, when a plurality of abbreviatedidentifiers are allocated to a mobile station. It is likewise possibleto keep the delay times short on the basis of a corresponding selectionof specific abbreviated identifiers at the end of a macro frame. Thelimitation of the number of abbreviated identifiers leads to a fasterre-employment of a time slot for signaling for a mobile station and to ashortening of the delay time. The plurality of abbreviated identifiersis advantageously set according to the transmission conditions and thenumber of mobile stations provided for the packet data service.

When a plurality of time slots for signaling are combined in downstreamdirection to form a signaling block, then the signaling advantageouslyoccurs simultaneously for a plurality of mobile stations. The signalingin downstream direction, however, can likewise occur within packet dataso that, for example, the transmission power setting can be continuouslyadapted without utilizing time slots for signaling and additional timeslots are available for neighboring cell measurement.

The signaling outlay also can be lowered by the selection of specifictransmission block types. When normal transmission blocks (normalbursts) are employed by contrast to what are referred to as accessbursts, an identification of reception power is possible by averagingover a greater plurality of bits, as a result whereof the measuringprecision is increased or, respectively, a lower number of repeatedmeasure values is required for setting the transmission power. Suchlonger transmission blocks are advantageously employed for setting thetransmission power when valid values for the timing advance are alreadypresent.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the Detailed Description of thePreferred Embodiments and the Drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 shows a block circuit diagram of a time-division multiplex mobileradio telephone system for packet data transmission;

FIG. 2 shows a frequency channel with time-division multiplex;

FIG. 3 shows the time slots of a channel for a packet data transmission;and

FIG. 4 shows the utilization of time slots for signaling (Tables 1, 2and 3).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The time-division multiplex mobile radio telephone system according toFIG. 1 is, for example, a GSM mobile radio telephone network GSM thatcontains at least one base station system BSS with a control means BSCand a base station BS. Mobile stations MS are located in the radiocoverage area of the one illustrated base station BS. The base stationsystem BSS produces the connection to further devices of the GSM mobileradio telephone network GSM.

These further devices are, for example, a mobile switching center MSCand a unit for realizing inter-working functions IWF. The collaborationof mobile switching center MSC and inter-working functions IWF yields apacket switching center that is also referred to as GSN (GPRS supportnode). This packet switching center is connected to an MSC for voicecommunication; alternatively, it could be realized as a separate, offsetunit.

The GSM mobile radio telephone network GSM can be connected to furthercommunication networks. For example, a further communication terminalequipment KEG is connectable to the GSM mobile radio telephone networkor is itself a component part of this GSM mobile radio telephone networkGSM.

The GSM mobile radio telephone network GSM should be utilized for packetdata transmission in parallel with known voice transmission. The meansfor realizing inter-working functions IWF can thereby produce thecoupling of the GSM mobile radio telephone network GSM with datatransmission networks and, thus, with the further communication terminalequipment KEG.

The radio interface between the mobile stations MS and a base station BSis characterized by a frequency and at least one time slot ts. Accordingto FIG. 2, for example, eight time slots ts (ts0 through ts7) arecombined to a frame R. The frame R repeats cyclically, whereby arecurring time slot, for example the time slot ts=ts4, belongs to achannel. This time slot ts is subsequently employed as channel GPRS-Kfor the packet data transmission for the purpose of the service GPRS(general packet radio services).

When a mobile station MS is to use this service, then it implements arandom access according to the GSM terminology with a short, so-calledaccess burst and switches to a dedicated control channel. Anauthentification at the setting of the context with respect to a logicalconnection (standby state) follow. When the further communicationterminal equipment KEG is to communicate with a mobile station MS viathe packet data service, a call (paging) as well as the described randomaccess occur at the network side.

When the mobile station MS is to transmit or receive data packets (readystate), a further random access occurs given the existence of a logicalconnection. An abbreviated identifier id and the corresponding GPRSchannel GPRS-K is thereby allocated to the mobile station MS. Whereuponthe timing advance ta and the reception level pb in the base station BSare identified at the network side, the mobile station MS is assignedfour successive time slots T as a packet data block TCH in upstreamdirection. Potentially, a particular regarding the transmission powercontrol is additionally transmitted.

The packet data transmission and the appertaining signaling shall now beshown with reference to FIG. 3 and to Tables 1 through 3.

Respectively, four time slots T for packet data transmission arecombined to form a packet data block TCH. Three such packet data blocksTCH and a time slot A, I for signaling repeat four times to form a macroframe that covers 52 frames R. This is true both of the upstream as wellas of the downstream direction. Further, two such macro frames in turnform a frame of a higher order. A macro frame lasts 240 ms.

The information of a packet data block TCH with four time slots T areinterleaved. The allocation of packet data blocks TCH to differentmobile stations MS ensues in upstream and downstream direction flexiblyon to one or more mobile station MS. Different data rates can thus berealized. One can distinguish between the mobile stations MS via theaccess to the GPRS channel on the basis of prioritizations. Upstreamdirection and downstream direction shall be considered separately below,whereby a mobile station MS can definitely communicate in bothdirections. The allocation of packet data blocks TCH during theexistence of a logical connection occurs in the band, i.e. who can usethe following packet data blocks TCH is indicated to the mobile stationsMS by indicator messages within the packet data blocks TCH.

Not only are four successive time slots T for packet data transmissioninterleaved in the downstream direction, but an interleaving of thesignaling information that form a signaling block GACCH also occurs.According to FIG. 3, every second time slot A for signaling is combinedto form the signaling block GACCH, during which time intervening timeslots I are employed for measurements of the mobile stations MS inneighboring cells. The sequence of time slots A, I for signaling andneighboring channel measurement also can follow a different sequence;for example, A/I=⅓. A switching of the sequences is undertaken by thebase station BS according to the transmission conditions.

The neighboring cell measurements serve for determining base stations BSthat can be selected given a deterioration of the transmissionconditions on the momentarily allocated channel. A priority list ispresent in the mobile station on the basis of these measurements.

A signaling block GACCH thereby contains information for several mobilestations MS, see Table 1 and Table 2 with respect thereto.Alternatively, measured to Table 3, it is possible to reduce theplurality of time slots per signaling block GACCH and, in addition to oras an alternative to an interleaving, to multiply transmit theconfiguration data (timing advance TA and/or transmission power settingPC) in a time slot or, respectively, to provide it with a furtherprotection; for example, with an encoding.

The inventive method is particularly advantageous when only adetermination of timing advance is undertaken and is signaled asdescribed below. The determination of transmission power occursindependently thereof. The higher flexibility in the configuring of theradio interface arises on the basis of such a separation of thedetermination of the two configuration data TA, PC. For simplification,however, an identical control circuit in the determination of timingadvance TA and transmission power setting PC shall be assumed below.

For example, the GACCH block contains the values for the timing advanceTA and the transmission power setting PC (for example, the receptionlevel of the base station BS or the required transmission power) for themobile stations 1 through 4. In this case, the duration until therepetition of the timing advance TA and of the transmission power valuesPC amounts to 480 ms. When a signaling occurs only for two mobilestations, for example two mobile stations that transmit in upstreamdirection, the number of abbreviated identifier id can be reduced to twoand the delay time now amounts to 240 ms.

The allocation of the time slots A for signaling in upstream directionoccurs as follows. According to Table 1, the allocation of the timeslots A0 through A1 for the mobile stations 1 through 2 occurs in theupstream direction (abbreviated identifiers id 0 through 1) and theallocation of the time slots A2 through A3 for the mobile stations MS 2through MS 3 occurs in the downstream direction (abbreviated identifiersid 2 through 3). When the mobile stations MS communicate both in theupstream and in the downstream directions, then the allocation of thetime slots A for signaling occurs according to Table 2.

Given the allocation according to Table 1, i.e. the separateconsideration of upstream direction and downstream direction, eachmobile station MS transmits a specifically encoded access burst to thebase station BS in the time slot A for signaling that is allocated toit. The field strength and quality (RXLEV, RXQUAL) with which thesignaling blocks GACCH of the base station BS were received in thedownstream direction are signaled therein. The base station BS measuresthe transmissions (allocated time slots A for signaling) of the mobilestations MS in order to determine a timing advance TA and a transmissionpower or, respectively, the transmission power change PC of the mobilestation and to signal it to it. The mobile station MS thus receivesvalues that it uses when packet data blocks TCH are transmitted in theupstream direction.

The base station BS uses the reception levels pm reported from themobile station MS to set an appropriate transmission power when packetdata blocks TCH for the data transmission are subsequently transmittedin the downstream direction to the mobile station MS. The followingdelay times derive for the current nature of the timing advances TA andtransmission power values in the upstream direction: the mobile stationMS receives new values at the spacing of 480 ms. Care is exercised inthe sequence of the time slots I, A to see that the time betweensignaling in the upstream direction by a mobile station MS and atransmission provided for this mobile station MS in the downstreamdirection is short.

According to Table 3, the signaling in the downstream direction wasfashioned such that every mobile station 1 through 4 was assigned anindividual time slot A for signaling in which the timing advance TA istransmitted with an additional error protection. All the fewer such timeslots A for signaling are required the fewer mobile stations use thecommon channel GPRS-K and all the more time slots I are available forneighboring cell measurements, for additional signaling (for example,connection cleardown, frequency change) or for an additional datatransmission.

The exemplary embodiments can be modified to the effect that abbreviatedidentifier id are employed such that the abbreviated identifier ids 1or, respectively, 3 is used with priority. In this case, delay timesclose to the best case of 240 ms derive. Even given a double employmentof abbreviated identifier id, the spacing between the arrival of newvalues is diminished. When the number of abbreviated identifiers islimited further, then the delay time is also shortened. When values thathave not been updated are acceptable for longer times, then the numberof abbreviated identifiers id also can be incremented in steps of fourto 8, 12, 16, etc.

The assigning of the abbreviated identifiers id is, in particular,adapted to the transmission conditions; i.e., to the previouslyregistered modifications of timing advance TA and transmission powerchanges. How many mobile stations MS wish to use to the packet datatransmission via the GPRS channel GPRS-K is also taken intoconsideration.

Due to the fixed allocation of time slots A for signaling in theupstream direction, the base station BS is always informed about thecurrent transmission conditions of the radio interface and can undertakea corresponding configuration of the radio interface. A closed controlcircuit exists for mobile stations MS that signal in this way inupstream direction and to which the values for the timing advance TA andfor the transmission power setting PC are communicated in the downstreamdirection via the signaling blocks GACCH. The control circuit is alsopossible when the mobile station MS does not transmit or receive anypacket data at the moment.

When, however, packet data blocks TCH in the upstream or downstreamdirections are also allocated to the mobile station MS, values for thetiming advance TA or the reception level pb, additionally can becalculated therefor and can be transmitted.

In particular, the packet-oriented transmission of the information viathe radio interface is suited for telematic applications, fax and datafile transmission, point of sales realizations, fleet management andtraffic routing systems.

Indeed, although the present invention has been described with referenceto specific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the invention as set forth in the hereafter appended claims.

We claim:
 1. A method for configuring a radio interface between a mobilestation and a base station of a time-division multiplex radio system fora packet data transmission, the method comprising the steps of: defininga transmission from a mobile station to the base stations as an upstreamdirection; defining a transmission from the base station to a mobilestation as a downstream direction; forming a channel by at least onetime slot per time-division multiplex frame; effecting the packet datatransmission of a plurality of mobile stations via the channel whereineach of the plurality of mobile stations is referenced with anidentifier; providing a time slot for signaling in the channel atcyclical intervals; identifying the plurality of mobile stations withabbreviated identifiers for the packet data transmission that areunambiguous in the channel; assigning exclusively, by the base station,at least one time slot for signaling for the upstream direction in acycle with all time slots for signaling to the mobile station accordingto a prescribable sequence; and allocating exclusively at least one timeslot for signaling for the upstream direction by indicator messages thatcontain the abbreviated identifiers and time slot designations, whereinthe allocation is independent of the packet data transmission from or tothe mobile station.
 2. A method for configuring a radio interfacebetween a mobile station and a base station as claimed in claim 1,further comprising the step of: allocating one or more abbreviatedidentifiers to a mobile station according to transmission conditions. 3.A method for configuring a radio interface between a mobile station anda base station as claimed in claim 1, further comprising the step of:setting the plurality of abbreviated identifiers for a channel accordingto transmission conditions.
 4. A method for configuring a radiointerface between a mobile station and a base station as claimed inclaim 1, further comprising the step of: limiting the plurality ofabbreviated identifiers for a channel to less than or equal to
 4. 5. Amethod for configuring a radio interface between a mobile station and abase station as claimed in claim 1, further comprising the step of:combining a plurality of time slots for signaling to form a signalingblock.
 6. A method for configuring a radio interface between a mobilestation and a base station as claimed in claim 5, further comprising thestep of: combining the time slots for signaling according to aprescribable sequence, wherein remaining time slots are provided for aneighboring cell measurement of the mobile stations.
 7. A method forconfiguring a radio interface between a mobile station and a basestation as claimed in claim 1, further comprising the step of: providinginformation in time slots for signaling with an additional encoding. 8.A method for configuring a radio interface between a mobile station anda base station as claimed in claim 1, wherein the packet datatransmission in the upstream direction occurs independently of thepacket data transmission in the downstream direction.
 9. A method forconfiguring a radio interface between a mobile station and a basestation as claimed in claim 1, wherein the configuration of the radiointerface occurs by the base station without control by a base stationcontroller.
 10. A base station system for configuring a radio interfacebetween a mobile station and a base station of a time-division mobileradio telephone system for packet data transmission, comprising: a basestation; a plurality of mobile stations, wherein a transmission from amobile station to the base station is defined as an upstream directionand a transmission from the base station to a mobile station is definedas a downstream direction; a channel formed by at least one time slotper time-division multiplex frame, wherein the packet data transmissionof the plurality of mobile stations occurs via the channel and each ofthe plurality of mobile stations is referenced with an identifier; atime slot for signaling provided in the channel at cyclical intervals;and a control means for the allocation of time slots to the plurality ofmobile stations, wherein the plurality of mobile stations are identifiedwith abbreviated identifiers for the packet data transmission that areunambiguous in the channel, wherein one or more time slots for signalingfor the upstream direction in a cycle with all time slots for signalingare exclusively assigned by the base station to the mobile stationsaccording to a prescribable sequence, wherein the exclusive allocationof one or more time slots for signaling for the upstream directionoccurs by indicator messages that contain abbreviated identifiers andtime slot designations, and wherein the allocation is independent of thepacket data transmission from or to the mobile station.